West Pacific/2015/11W/Archive/7
Public advisory TROPICAL STORM NANGKA PUBLIC ADVISORY NUMBER 7 WIKI-HURRICANES FORECASTING CENTER 12:00 PM JST SUN JUL 06 2015 ...SCATTEROMETER INDICATES NANGKA IS A STRONGER SYSTEM... SUMMARY OF 12:00 PM JST...03:00 UTC...INFORMATION ------------------------------------------------------------------- LOCATION...11.4N, 164.3E CENTER POSITION CONFIDENCE: HIGH ... ± 20 MI... 30 KM ABOUT 520 MI...835 KM NE OF PALIKIR, MICRONESIA MAXIMUM SUSTAINED WINDS...50 KT...60 MPH...95 KM/H MINIMUM BAROMETRIC PRESSURE...998 MB...29.47 INCHES PRESENT MOVEMENT...WNW AT 8 KT...9 MPH...15 KM/H DISCUSSION AND 48-HOUR OUTLOOK --------------------------------------------- At 12:00 pm JST, the center of Tropical Storm Nangka was situated near 11.4N, 164.3E, or about 520 miles (835 kilometers) east-northeast of Palikir, Micronesia. Maximum sustained winds were 50 knots (60 mph, 95 km/h), with higher gusts. The minimum barometric pressure was 998 millibars (hPa; 29.47 inHg), and the cyclone was tracking west-northwest at 8 knots (9 mph, 15 km/h). Despite earlier indiciations that environmental conditions may not be conducive for marked strengthening, such indicators have trended towards a more conducive environment that may hint at the potential for steady if not rapid strengthening within the 48 hour timeframe. NEXT ADVISORY ------------------- Next complete advisory at 12:00 am JST. $$ Forecaster TheAustinMan Discussion TROPICAL STORM NANGKA DISCUSSION NUMBER 7 WIKI-HURRICANES FORECASTING CENTER 12:00 PM JST SUN JUL 06 2015 Despite unimpressive returns from satellite intensity estimates suggesting that Nangka has remained towards the low end of the tropical storm intensity spectrum over the past day, a ASCAT pass at 22:00z this morning revealed a quite different picture, detecting a sizeable area of 40 knot winds and even a patch of 50 knot winds. Typically, as a byproduct of its 25km resolution, the ASCAT instrument often undersamples the true intensity of a storm, but given the somewhat exposed low-level center of circulation and lower satellite intensity estimates, the intensity for this advisory will be set right at the 50 knots that ASCAT suggests, still a change upward from the last advisory. Nangka still possess a small central dense overcast near the center of circulation and a dominant spiral band to its west, with impressive transverse bands of cirrus outflow to the east. A void of deep convection exists between the core and the western rainband, and Nangka may be intaking dry air through this channel, though currently whether this is occuring or not is unknown. Modelling remains in good agreement in regards to the track of Nangka as the 594 dm subtropical ridge to its north remains the dominant steering force. Models are also in agreement that Nangka will gain latitude more quickly the further west it traverses as a result of a weakness in the ridge induced by a progressing trough. Given that none of these parameters has changed significantly, the current WHFC track forecast is virtually an update of the last. The intensity forecast continues to increase as the forecast atmospheric conditions continue to indicate more conducive conditions. Nangka currently lies in COAMPS-analyzed 8 knot shear, though the low level circulation center has been slightly outpacing the convection. With a slight slowdown anticipated, the convection should be able to redevelop over the center, which will be a better convective configuration to allow for strengthening. Assuming Nangka does not get caught up in the outflow of Chan-hom ahead of it, conditions are expected to continue to be conducive for strengthening. Shear is expected to increase to around 20 knots at around 36 hours before dropping quite dramatically afterwards, which will be suitable for perhaps quick strengthening during that timeframe. Models have trended quite aggressively in terms of Nangka's long term intensity, and thus the current WHFC forecast suggest that Nangka will take advantage of conducive conditions near the Mariana Islands. INIT 05/0300Z 11.4N 164.3E 50 KT 60 MPH ... NEAR MARSHALL ISLANDS 12H 05/1200Z 11.6N, 161.5W 55 KT 65 MPH 24H 06/0000Z 12.0N 159.4E 65 KT 75 MPH 36H 06/1200Z 12.7N 157.2E 70 KT 80 MPH 48H 07/0000Z 14.4N 154.6E 75 KT 85 MPH 72H 08/0000Z 16.9N 151.2W 85 KT 100 MPH 96H 09/0000Z 19.4N 146.9E 95 KT 110 MPH ... NEAR NORTHERN MARIANA ISLANDS 120H 10/0000Z 22.2N 142.2E 110 KT 125 MPH ... NEAR NORTHERN MARIANA ISLANDS $$ Forecaster TheAustinMan